Frank Hecker

Fun with Howard County building permit data

3 minute read

I have fun creating graphs and maps with building permit data from
data.howardcountymd.gov.

I’ve written previously about the cornucopia of interesting data
sets that Howard County government has made available at the
data.howardcountymd.gov site. I had some spare time over a long
weekend and decided to try analyzing some of that data, including
making use of the various map files on the site (under the “Spatial
Data (GIS)” tab).

The particular data set I decided to start with was for building
permits issued for residential and commercial construction—not
because I have a burning interest in building permits but because I
mentioned this type of data in my last post and thought it would be a
relatively easy data set to analyze. The particular question I decided
to look at was how many residential building permits were issued in
each zip code within Howard County in 2014—basically to get a feel
for where the most construction was occurring in the county. (It’s
only an approximate measure because some permits cover multiple
units.)

I first created a simple table of the top zip codes for residential
permits issued. This was sort of boring so I won’t reproduce it here;
you can find it in the first example
analysis I did. More interesting
is the bar chart I created as part of the second
example. It’s clear from the
chart that there’s wide variation among Howard County zip codes in
terms of residential construction. The two Ellicott City zip codes
combined (21042 and 21043) accounted for the largest fraction of
residential building permits in 2014; in contrast there were almost no
permits issued for east Columbia (21045).

However what I really wanted to create was a map showing exactly where
permits were being issued across the county. The Howard County GIS
division provides on data.howardcountymd.gov a set of map data for zip
codes within Howard County. After doing a bit of research and
experimentation, in my third
example I was able to use this in
conjunction with the building permit data to produce a map that is a
nice alternative to the bar chart.

I have to stop here and ask the unspoken question: What’s the point of
all this? I’d answer as follows:

First, this shows that releasing government data empowers people to do
interesting things with it, especially when combined with free
software and easily available online information and training. Maybe
everybody isn’t interested in building permit data or any other
individual government data set, but I suspect that there are a fair
amount of people out there who are, including small businesses,
nonprofit organizations, or just individual activists and interested
citizens.

Second, I did all this in a way that is completely reproducible by
anyone else. How often have you seen a graph or map in a newspaper or
government report and wondered, where exactly did that data come from?
Wonder no longer: In my examples I start with the raw data as released
by Howard County and show all my work in analyzing the data and
creating the tables, charts, and maps.

Finally, this is all reusable and adaptable. For example, suppose you
have a better source of data on construction activity, perhaps one
that gives the actual numbers of residential units, commercial square
footage, and so on. You can easily plug that modified data into the
analysis steps I’ve documented, and create better versions of the
charts and maps in my examples.

You can also reuse the overall technical approach for any type of data
tied to a geographic area within Howard County. For example, in
addition to zip code areas the data.howardcounty.gov site contains map
data for Howard County school districts, election precincts, census
tracts, and many other subdivisions of the county. If you have data
sets that are based on those subdivisions (for example, vote totals or
turnout percentages for precincts) then you can adapt the code I wrote
(all of which is in the public domain) to create your own maps showing
how that data varies across the county.

The bottom line is that the data is out there for the picking, as are
the tools to make sense of it. You just need to spend some time
learning how to use them or (if you don’t feel up to the task
yourself) finding someone who can. Have fun!